This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-278267 filed on Sep. 13, 2000 and Japanese Patent Application No. 2000-374763 filed on Dec. 8, 2000.
1. Field of the Invention
The present invention relates a motor having a noise limiter circuit for restraining generation of electromagnetic noise between brushes and a commutator.
2. Description of Related Art
In general, electromagnetic noise is generated between brushes and a commutator during rotation of a direct current motor. When power supplied to the brushes includes a relatively large amount of noise, a relatively large amount of electromagnetic noise is generated. Thus, some previously proposed motors have a noise limiter circuit that includes capacitors, choke coils and the like to smooth the electric power supplied to the brushes.
To reduce a size (thickness) of such a motor, it has been proposed to use an oblate cylindrical housing having a smaller profile in comparison to a cylindrical housing. In order to further reduce the size of the motor having the oblate cylindrical housing, effective arrangement of the electronic components, such as the choke coils, within the housing has been demanded.
Thus, it is an objective of the present invention to provide a motor that allows a reduction in its size by effective arrangement of its components.
To achieve the objective of the present invention, there is provided a motor including an electrically conductive yoke housing and a noise limiter circuit. The yoke housing is configured in an oblate cylindrical cup form having two opposed flat side walls and two opposed arcuate side walls, each of which joins corresponding opposed lateral edges of the flat side walls together. The yoke housing has an open end at one end and receives a plurality of brushes and a commutator. The noise limiter circuit is arranged at the open end of the yoke housing and smoothes electric power to be supplied to the plurality of brushes to restrain generation of electromagnetic noise between the plurality of brushes and the commutator. The noise limiter circuit includes at least one of the following components: a plurality of helically wound cylindrical choke coils and a plurality of capacitors. Each choke coil is arranged adjacent to a corresponding corner of the yoke housing located between a corresponding one of the flat side walls and a corresponding one of the arcuate side walls in such a manner that each choke coil extends substantially parallel to a central axis of the yoke housing. The capacitors are arranged adjacent to a center of one of the flat side walls.